As chances grow that the Supreme Court will take up the constitutionality of the 2010 health care law, a political battle is brewing over whether some justices should recuse themselves from what is likely to be a high-profile case.

Seventy-four House Democrats, led by New York Rep. Anthony Weiner, sent a letter to Justice Clarence Thomas Wednesday calling on him to sit out deliberations on the Affordable Care Act because of his wife's ties to a lobbying group that opposes the health care law.

"The appearance of a conflict of interest merits recusal under federal law," the letter said. "From what we have already seen, the line between your impartiality and you and your wife's financial stake in the overturn of healthcare reform is blurred."

Justice Thomas' wife, Virginia Thomas, founded the conservative group Liberty Central, but stepped down in December amid controversy over a memo under her name calling for the repeal of the "unconstitutional law."

The group, which later took down the memo from its site, blamed staff error and said it "assiduously avoids" taking positions on the constitutionality of issues.

Under federal law, justices have to recuse themselves from cases where they feel a conflict of interest may arise, or if their spouses have a financial stake in the case, but the decision ultimately rests with each justice.

"It's up to the individual justice to determine whether he believes that, in fact or appearance, there's sufficient concern about his impartiality to make recusal appropriate," said Deborah L. Rhode, a legal ethics scholar and professor of law at Stanford University. "So he [Thomas] should be considering whether he believes he can act in a disinterested manner, but also the court's credibility with the public, and will Americans, who may differ with him... believes he comes to the table with an unbiased view."

While it's not uncommon for justices to recuse themselves, there has been no case in recent history in which a justice has stepped aside because of a spouse-related conflict of interest.

But as the makeup of the Supreme Court changes, spousal connections are increasingly coming under scrutiny.

Justice Thomas, who has been on the Supreme Court since 1991, came under heavy criticism last month after reports emerged that he omitted his wife's place of employment in his financial disclosure forms.

Democrats Call on Justice Thomas to Recuse Himself from Health Care Proceedings

Justice Ruth Bader Ginsburg took similar heat several years ago for failing to disclose her husband's holdings in her financial disclosure forms.

Ginsburg, an 18-year veteran of the Supreme Court, has faced criticism in the past for not recusing herself from cases involving companies her husband, a tax attorney, has invested in.

Critics aren't just pointing to Thomas for having a conflict of interest in a potential health care case.

Sen. Orrin Hatch, R-Utah, has questioned the involvement of Justice Elena Kagan, a former member of President Obama's administration.

"I personally believe she should recuse herself. I'm sure she participated in discussions at the White House. Participated in discussions in the solicitor general's office. These issues were brought up throughout the process," Hatch said on Fox News last week. "That's going to be up to her what she does."

Kagan has recused herself from several cases since she was appointed to the Supreme Court last August.